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|
; Part of Scheme 48 1.9. See file COPYING for notices and license.
; Authors: Richard Kelsey, Jonathan Rees, Mike Sperber, Martin Gasbichler
; Implementation of OS channels in Scheme.
;
; A channel an index into a vector of ports in the underlying Scheme
; implementation.
; Vector mapping indicies to ports.
(define *channels* '#())
(define (vector-posq vec thing)
(let loop ((i 0))
(cond ((= i (vector-length vec))
#f)
((eq? thing (vector-ref vec i))
i)
(else
(loop (+ i 1))))))
(define (channel->port channel)
(vector-ref *channels* channel))
(define input-channel->port channel->port)
(define output-channel->port channel->port)
(define (port->channel port)
(or (vector-posq *channels* port)
(make-channel port)))
(define input-port->channel port->channel)
(define output-port->channel port->channel)
; Add PORT to the vector of channels, reusing a slot if possible.
(define (make-channel port)
(let ((channel (or (vector-posq *channels* #f)
(let ((channel (vector-length *channels*)))
(set! *channels* (list->vector
(append (vector->list *channels*)
(list #f #f #f #f))))
channel))))
(vector-set! *channels* channel port)
channel))
; The default ports
(define (current-input-channel)
(port->channel (current-input-port)))
(define (current-output-channel)
(port->channel (current-output-port)))
(define (current-error-channel)
(port->channel (current-error-port)))
; These just open or close the appropriate port and coerce it to a channel.
(define (open-input-file-channel filename)
(receive (port status)
(prescheme:open-input-file filename)
(if (eq? status (enum prescheme:errors no-errors))
(values (port->channel port) status)
(values #f status))))
(define (open-output-file-channel filename)
(receive (port status)
(prescheme:open-output-file filename)
(if (eq? status (enum prescheme:errors no-errors))
(values (port->channel port) status)
(values #f status))))
(define (close-input-channel channel)
(prescheme:close-input-port (channel->port channel)))
(define (close-output-channel channel)
(prescheme:close-output-port (channel->port channel)))
(define (channel-ready? channel read?)
(values (if read?
(char-ready? (channel->port channel))
#t)
(enum prescheme:errors no-errors)))
(define (channel-crlf?) #f)
;----------------
; Non-blocking I/O (implemented using CHAR-READY?)
;
; We keep a list of channels for which the user is waiting. These will
; all be input channels as CHAR-READY? only works on input ports.
(define *pending-channels* '())
(define (channel-read-block channel start count wait?)
(cond ((char-ready? (channel->port channel))
(receive (count eof? status)
(read-block (channel->port channel) start count)
(values count eof? #f status)))
(wait?
(set! *pending-channels* (cons channel *pending-channels*))
(values 0 #f #t (enum prescheme:errors no-errors)))
(else
(values 0 #f #f (enum prescheme:errors no-errors)))))
(define (channel-write-block channel start count)
(values count #f (write-block (channel->port channel) start count)))
(define (channel-buffer-size) 4096)
(define (channel-console-encoding channel) "ISO8859-1")
(define (channel-abort channel)
(set! *pending-channels* (delq channel *pending-channels*))
0)
;----------------
; Events
;
; A keyboard interrupt can be generated by setting the following to #t.
(define *pending-keyboard-interrupt?* #f)
(define (initialize-events)
(set! *channels* (make-vector 10 #f))
(set! *pending-channels* '())
(set! *pending-keyboard-interrupt?* #f))
(define (pending-event?)
(or *pending-keyboard-interrupt?*
(any? (lambda (channel)
(char-ready? (channel->port channel)))
*pending-channels*)))
; The event enumeration is copied from the C version of this code.
(define-enumeration events
(keyboard-interrupt-event
io-completion-event
io-error-event
alarm-event
os-signal-event
error-event
external-event
no-event
))
(define (get-next-event)
(cond (*pending-keyboard-interrupt?*
(set! *pending-keyboard-interrupt?* #f)
(values (enum events keyboard-interrupt-event) #f #f))
((any (lambda (channel)
(char-ready? (channel->port channel)))
*pending-channels*)
=> (lambda (channel)
(set! *pending-channels* (delq channel *pending-channels*))
(values (enum events io-completion-event)
channel
0)))
(else
(values (enum events no-event) #f #f))))
(define (wait-for-event max-wait minutes?)
(breakpoint "Waiting"))
|
